James DeGale will spend a week sparring with Nathan Cleverly as both Frank Warren stars prepare for massive fights on May 21 at the O2 Arena.
Cleverly will travel to DeGale's base for the seven-day stint.
The pair have previously sparred in South Wales.
DeGale takes on George Groves at the O2 Arena in a British and Commonwealth super-middleweight title showdown.
And interim WBO light-heavyweight champion Cleverly will box for the full WBO title against Jurgen Braehmer.
"Cleverly's a very good fighter, and he'll be perfect preparation for Groves," said DeGale.
"I didn't realise how good he was until we worked together last year. I was very impressed with him and he's got a massive talent.
"I sparred him and Tony Bellew, and they're probably the hardest spars I've had."
DeGale will also draft in former European middleweight champion Darren Barker, while he also hasn't one day ruled out meeting Cleverly.
The pair are a weight division apart at the moment, but DeGale could end up at light-heavy.
"We're friends, I see him at events and we text each other," said DeGale.
"But you can never say never in boxing. If we keep on winning then a fight between the pair of us will get bigger and bigger."Tags: British Boxing , James DeGale , George Groves , Nathan Cleverly , DeGale vs Groves , DeGale-Groves , Darren Barker